"Rear focal distance" redirects here. For lens to film distance in a camera, see Flange focal distance.
The focal length of an optical system is a measure of how strongly the system converges or diverges light. For an optical system in air, it is the distance over which initially collimated rays are brought to a focus. A system with a shorter focal length has greater optical power than one with a long focal length; that is, it bends the rays more strongly, bringing them to a focus in a shorter distance.
In most photography and all telescopy, where the subject is essentially infinitely far away, longer focal length (lower optical power) leads to higher magnification and a narrower angle of view; conversely, shorter focal length or higher optical power is associated with a wider angle of view. On the other hand, in applications such as microscopy in which magnification is achieved by bringing the object close to the lens, a shorter focal length (higher optical power) leads to higher magnification because the subject can be brought closer to the center of projection.
Is that a better general explaination?
The flowers are not moving
The dog is moving
Upgrades are good
To freeze the action of movement us Shutterspeed of 500 of more
AF takes time to adjust
Candid shots don't support using AF
For candids like this it is easier to preset your Ss and F/S, then focus area is already in place for given space. Simply make sure you are the proper distance from your subject for your settings.
Two different days
Two different fields-of-vision
Two different skys
The list goes on...
First Guess:
White balance may be off
Second Guess:
Under exposed
Third Guess:
God is upset with you (Ha Ha)
35mm lens should work well for you re both cases.
Two different ways exists...
Item One:
Household insurance coverage
Item Two:
Professional Use insurance
Two different considerations
Often, focal length refers to the distance between the front and back element of a given lens. It also provides a reference to the angle/area of coverage and magnification provided by the lens.
It gets more complicated but this is the basic understanding.
Keep Shooting,
John A
DOF or Depth of Field refers to the area of focus behind and infront of the subject your primary focus point is on. DOF is mainly controlled by the F/Stop setting.
The DOF is controlled by the F/Stop.
The bigger your F/Stop number is the larger your DOF becomes.
The smaller your F/Stop equates to the smaller your DOF becomes. Quick reference: F/2.8 ='s small DOF, F/16 and up ='s greater DOF.
Shutter speed (S/S) has very little to do with DOF. However, S/S does affect DOF when you are using very long S/S such as when you are using a "B" Bulb type setting or a very long exposure, say a 2min exposure. Nevertheless, S/S in general does not affect DOF when your exposure is under 1min exposure.
In your picture of the girl with bubbles it is visually evident your DOF is just a bit narrow so as to capture both the bubbles and the young girls face in sharp focus. (Bubbles are sharp, Girl's face is slightly out of sharp focus.)
Not knowing the F/Stop you used for this photo makes it difficult to nail the answer on the head. However, it is safe to say that based on the image, you are only .5 to 1 stops from nailing the area of focus you desire.
Example: If you used, let us say, F/11 to snap the image, then you should increase your DOF by changing your F/Stop from F/11 to F/11 - F/16 or one full stop to F/16. That adjustment should now capture the bubbles and the girl's face in sharp focus.
Keep in mind the following: F/Stops provide adjustment not only between whole numbers printed on the adjustment ring, such as from F/11 to F/16 or from F/11 to F/8.
F/Stops are also functional at all points between noted/printed numbers. An example would be setting your F/Stop manually toF/11-F/16 or F/11-F/8. These settings would represent HALF F/Stop adjustments. Quarter adjustments are also available via F/Stops when setting them manually.
Also, use of a hand-held light meter, not the light meter located in the camera, will assist you in easier nailing of your exposures if you so desire. As for knowing the DOF of any lens at a given F/Stop will be found in the techinical data for the lens being used.
Further, on a related topic, data for each image you create digitally normally is captured in the EXIF data with the image. This information can be seen by using BRIDGE or other available software used to view your image data. You can search the web and download a free copy of this particular type of sofware to your computer. You may want to become familiar with this type of software for future reference and use.
Good Shooting,
JohnA